This invention generally relates to intraluminal stents and vascular catheters suitable for maintaining the patency of a blood vessel after a vascular procedure therein, such as angioplasty.
In typical percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient through the brachial or femoral arteries and is advanced therein until the distal tip thereof is in the ostium of the desired coronary artery. A guidewire and a dilatation catheter having an inflatable balloon on the distal end thereof are introduced through the guiding catheter with the guidewire slidably disposed within an inner lumen of the dilatation catheter. The guidewire is first advanced out of the distal end of the guiding catheter and is maneuvered into the patient's coronary vasculature containing the lesion to be dilated, and is then advanced beyond the lesion. Thereafter, the dilatation catheter is advanced over the guidewire until the dilatation balloon is located across the lesion. Once in position across the lesion, the balloon of the dilatation catheter is filled with radiopaque liquid at relatively high pressures (e.g., greater than about 4 atmospheres) and is inflated to a predetermined size (preferably the same as the inner diameter of the artery at that location) to radially compress the atherosclerotic plaque of the lesion against the inside of the artery wall to thereby dilate the lumen of the artery. The balloon is then deflated so that the dilatation catheter can be removed and blood flow resumed through the dilated artery.
By way of example, further details of angioplasty procedures and the devices used in such procedures can be found in U.S. Pat. No. 4,323,071 (Simpson, et al.), U.S. Pat. No. 4,332,254 (Lundquist), U.S. Pat. No. 4,439,185 (Lundquist), U.S. Pat. No. 4,168,224 (Enzmann, et al.), U.S. Pat. No. 4,516,972 (Samson), U.S. Pat. No. 4,582,181 (Samson), U.S. Pat. No. 4,538,622 (Samson, et al.), U.S. Pat. No. 4,597,755 (Samson), U.S. Pat. No. 4,616,652 (Simpson), U.S. Pat. No. 4,748,982 (Horzewski, et al.), U.S. Pat. No. 4,771,778 (Mar), and U.S. Pat. No. 4,793,350 (Mar, et al.) which are hereby incorporated herein in their entirety.
A common problem that sometimes occurs after an angioplasty procedure is the appearance of restenosis at or near the site of the original stenosis in the blood vessel which requires a secondary angioplasty procedure or a bypass surgery. Another occurrence which reduces the success of an angioplasty procedure is that frequently the stenotic plaque or intima of the blood vessel or both are dissected during the angioplasty procedure by the inflation of the balloon. Upon the deflation of the balloon, a section of the dissected lining (commonly termed "flap") will collapse into the bloodstream, thereby closing or significantly reducing the blood flow through the vessel. In these instances, emergency bypass surgery is sometimes required to avoid a myocardial infarct distal to the blockage.
Conceivably, the dilatation catheter could be replaced with a perfusion type dilatation catheter such as described in U.S. Pat. No. 4,790,315 in order to hold the blood vessel open for extended periods. However, perfusion type dilatation catheters have relatively large profiles which can make advancement thereof through the blockage difficult, and therefore immediate bypass surgery may be the only means of avoiding an infarct distal to the blockage or possibly even death. Additionally, the inflated balloon of these perfusion catheters can block off a branch artery, thus creating ischemic conditions in the side branch distal to the blockage.
In recent years, various devices and methods (other than bypass surgery) for prevention of restenosis and repairing damaged blood vessels have become known which typically use an expandable cage or region (commonly termed "stent") on the distal end of the catheter designed to hold a detached lining against an arterial wall for extended periods to facilitate the reattachment thereof. Some stents are designed for permanent implantation inside the blood vessel and others are designed for temporary use inside the vessel. By way of example, several stent devices and methods can be found in U.S. Pat. No. 4,998,539, U.S. Pat. No. 5,002,560, U.S. Pat. No. 5,034,001 (Garrison, et al.), U.S. Pat. No. 5,133,732 (Wiktor), and U.S. Pat. No. 5,180,368 (Garrison).
Typically, the expandable region of these stents is formed by a braided wire attached to the distal end of the catheter body. Such braided designs are difficult and expensive to manufacture, and can create reliability concerns due to the existence of high stress points located at the connection of the braided wire region with the catheter body and at the connections between the intermingled wire strands.
Alternatively, the expandable stent can be formed by a helical metal or plastic spring that is mechanically restrained in a contracted state during delivery to a predetermined position within a vessel. After placement, the mechanical restraint is released, allowing the helical spring stent to expand rapidly against the inner walls of the vessel. Examples of such stents are disclosed in U.S. Pat. No. 4,768,507 (Fischell, et al.), U.S. Pat. No. 4,990,155 (Wilkoff), and U.S. Pat. No. 4,553,545 (Maass, et al.). Each of these patents discloses a method for percutaneous transluminal insertion of a coiled stent that is mechanically restrained until released. Each system requires axial displacement of the delivery system to release the coiled stent and to disengage the stent from the catheter. The disadvantage of the axial displacement is the possibility that the additional intravascular manipulation and translation required to disengage the coiled stent from the delivery device may lead to undesirable damage to the vessel walls.
What has been needed and heretofore unavailable is an easily advanceable and removable low-profile intravascular catheter which can simply deliver a coiled stent to hold a collapsed dissected lining or flap against the blood vessel wall for sufficient time to allow the natural adhesion of the flap to the blood vessel wall and to aid in the prevention of restenosis while simultaneously allowing for the perfusion of blood to locations distal to the stent without blocking a branch vessel. The present invention fulfills this need.